Re: [Lsvr] [Tsv-art] Tsvart early review of draft-ietf-lsvr-l3dl-03

Randy Bush <randy@psg.com> Tue, 26 May 2020 06:04 UTC

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Subject: Re: [Lsvr] [Tsv-art] Tsvart early review of draft-ietf-lsvr-l3dl-03
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>>>>>>> 3. When the protocol applies fragmentation, should there be a note on
>>>>>>> preventing bursts?
>>>>>> likely part of this is our fault, as we did not mean 'fragmentation' in
>>>>>> the classic "oops!  we found a hop with a small mtu."
>>>>> I didn't take it to mean classic fragmentation but rather ALF-style
>>>>> operation.  Still, this could generate bursts depending on how much
>>>>> information there is to 'fragment'.
>>>> yes, it is app level framing.  perhaps we should call it that explicitly
>>>> or even segmentataion or some term less well known.
>>>> do you perhaps have a specific suggestion?
>>> Not really.  This all appears artificial if you need two or three
>>> packets for app layer fragmentation.  Maybe one could write something
>>> substantially improved along the lines of:
>>> To prevent packet bursts, a sender SHOULD pace the transmission of
>>> application layer fragmented data units as follows: A sender MAY
>>> transmit up to K packets containing fragments in a burst and SHOULD
>>> pace bursts ... (but how?)
>> 
>> ok.  i have stared at this three times today and have no bright ideas.
>> i do not want to start pacing by measuring rtt or other known deep
>> holes.  so i will try to think some more.
>> 
> 
> One option could be to just have a note of warning.  Any ideas how big
> your application layer messages will usually get...?

as you pointed out up-thread, a few frames.  a dozen would be highly
unlikely.  but, it's the internet; so you never know.

randy